Comparative study of the transient emission profiles of a light-duty vehicle powered by petrodiesel and a light-duty vehicle powered by biodiesel (Jatropha curcas)

摘要

Jatropha curcas biodiesel was produced via transesterification in the presence of acid catalysts. The fatty acid compositions of the biodiesel were determined using gas chromatography and mass spectroscopy. The emission features of a light-duty vehicle fuelled with Jatropha curcas methyl ester and a light-duty vehicle fuelled with petrodiesel fuel were compared in transient operating modes. In comparison with petrodiesel, under the standard test cycle, the hydrocarbon emissions, the carbon monoxide emissions and the particulate matter emissions from the vehicle fuelled with Jatropha curcas methyl ester were decreased by 57.5%, 40.8% and 42.7% respectively, owing to the 11% oxygen content in the biodiesel; however, the nitrogen oxide emissions increased by 4.9%. The regularity of the nitrogen oxide emissions in the transient operating mode are characterized by an innovative term, namely the volumetric concentration ratio of nitrogen oxide to carbon dioxide. The correlations of the transient nitrogen oxide emissions with the carbon dioxide emissions, the fuel consumptions and the operating modes are comprehensively analysed. In the constant-speed mode, the nitrogen-oxide-to-carbon-dioxide ratio becomes stabilized at a relatively low level but rises to a peak under transient conditions. This behaviour particularly occurs when the constant-speed mode shifts to an acceleration operation and when a deceleration operation shifts to a constant-speed mode. During the transient shifting stage, the nitrogen-oxide-to-carbon-dioxide ratio of the biodiesel vehicle is greater than that of petrodiesel vehicle; however, the nitrogen-oxide-to-carbon-dioxide ratios are only slightly different in the stable operating mode.